There is a critical need for objective markers of progression from genital tract infection to tissue damage resulting in morbidities of chronic pelvic pain, infertility, ectopic pregnancy and premature delivery. The long term goal of the proposed research is to develop methods to prevent sexually transmitted infection and reproductive tract sequelae in women exposed to sexually transmitted pathogens that cause pelvic inflammatory disease (PID). The central hypothesis is that biomarkers that predict development of reproductive tract disease or genetic markers of increased risk are present in host inflammatory and repair (fibrogenic) pathways. The objective of this application is to identify these key pathways and develop and validate a predictive clinical instrument based on these biomarkers, with the rationale that this tool can be used to identify vulnerable individuals. To identify candidate biomarkers and risk factors to be integrated into a predictive tool and to test our hypothesis we will pursue the following specific aims during the R21 phase of this proposal: (1) Identify the local inflammatory and fibrotic pathways most strongly regulated during Chlamydia trachomatis infection by performing microarray-based analysis of RNA isolated from endometrial tissue biopsies obtained from women with symptomatic PID. (2) Identify markers for susceptibility to C. trachomatis infection and for progression to tubal pathology by analysis of single nucleotide polymorphisms (SNPs) linked to incidence and severity of STI. This contribution is significant because development of this screening tool will directly benefit individuals diagnosed with active STI by identifying those at risk for sequelae arising from even asymptomatic infection. The proposed research is innovative because it combines two complimentary approaches for the identification of biomarkers associated with PID and its sequelae. Achievement of critical milestones: (1) a PID transcript signature, and (2) SNPs associated with genetic traits that predispose to infection and tubal pathology will drive transition to the translational R33 phase of the proposed research. This will include an unbiased Genome Wide Association Study (GWAS) to find genetic variations that further define risk for sequelae and evaluation of a panel of protein candidate biomarkers for their ability to predict inflammation and disease in a clinical setting. In the concluding years, all of the data will be integrated to develop a predictive model that will be tested using two geographically defined cohorts of women at high risk for STI and reproductive tract disease. This contribution is significant because development of this screening tool will directly benefit individuals diagnosed with active STI by identifying those at risk for sequelae arising from even asymptomatic infection. It also has broad application to evaluation of novel vaccines and interventions to prevent reproductive morbidities.